Cubic carbon would be very hard, it can be made at all. It could hold an incredibly sharp edge. The blade of a Katana is usually made of folded carbon steel, but with carbon fibre and graphene string to make and wrap the handle and guards, composites of carbon nanotubes, graphene and cubic carbon for the blade, and a cubic carbon edge, with maybe a few diamonds and graphite patterning to decorate Carbon Girl’s Katana, a pure carbon Katana could be made for both her and Carbon Man. No other materials are needed at all.

Perfect. But if they aren’t allowed to take them with them for some reason, they can quickly fabricate temporary but lethal substitute using nothing more than carbon tape.

I have a toy gun that fires spinning foam disks. It is pretty harmless of course. But it gave me an idea for the armory. Swords are fine for close up engagements, but a gun is hard to beat at a distance.

A graphene disk would be ideal for high-speed projection. The material of the disk would support high electric currents and therefore magnetic field interaction with the gun. Without bothering with too much detail, a future professional version of a disk gun could be made that fires ultra-thin (sharp) but highly strong graphene disks, spinning at high speed, and having minimal air resistance.

So the disks would shoot quite far, and self stabilising so fairly accurate, and very sharp, so would do damage. A high-speed cluster of them could be used to good effect to significantly damage or impede an enemy.

Electromagnetic forces could also be used to fire graphene darts. No new concepts are needed, the rail gun already exists and that mechanism would be perfect at any scale. Darts would scale too. Small darts with just a few layers of graphene would be very lightweight so convey limited mechanical damage, even if travelling fast, so they may be best suited for puncturing and short circuiting electrical equipment. Thicker and heavier ones would be much more lethal, adding mass and strength using any carbon material in the center, and being very streamlined and sharp if they taper the number of layers at the edges.

Cubic carbon is a fanciful material that may not even be possible to fabricate, using all 6 electrons to form bonds with neighbors in a cubic structure. It should be extremely hard, and such a material would be useful to make or add tips or edges to projectiles that could pierce or damage anything.